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- Biology Definition: Respiration is a chemical reaction that happens in all living cells. (Both plant cells and animal cells). Respiration is the way that energy is released from glucose so that all the other chemical processes needed for life can happen.
- Normal definition: The action of breathing, also called ventilation.
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Answer: Serotonin
Explanation:
Serotonin is an hormone, derived from the amino acid, tryptothan. It is involved in vasodilation, sleep regulation, mood changes, capillary permeability, and causes contraction of smooth muscles like that of the stomach to signal hunger.
Answer:
click on the photo. this should help. please mark brainliest:)